Device for measuring an aortic valve annulus in an expanded condition

ABSTRACT

An orifice-expanding device for measuring an expanded heart valve. The device includes a proximal handle having a shaft and an orifice-expanding device with a hub mounted to a distal end of the shaft and a plurality of arms evenly spaced around the axis and connected to the hub and extending therefrom in a distal direction to distal ends of the arms. The distal end of each arm has an expanding portion with an outer surface, the expanding portions being configured to move radially outward with respect to each other, wherein expansion of the expanding portions causes the distal ends of the arms to flex outward. A pressure-measuring device measures a pressure applied to the aortic valve annulus, and a size-measuring device measures a dimension of the aortic valve annulus after the annulus has been expanded.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.15/462,386, filed Mar. 17, 2017, now U.S. Pat. No. 10,231,646, which isa continuation of U.S. patent application Ser. No. 13/762,232, filedFeb. 7, 2013, now U.S. Pat. No. 9,603,553, which is a continuation ofU.S. application Ser. No. 12/606,945, filed Oct. 27, 2009, now U.S. Pat.No. 8,449,625, the entire disclosures of which are incorporated byreference.

FIELD

The present application relates to a system for measuring orifices andpassageways in the human body, including, for example, heart valveannuli.

BACKGROUND

The accurate measurement of orifices and passageways in the human bodyis important for the success of a variety of medical procedures. Inparticular, accurate measurement of the anatomy of the human body isoften crucial for the successful implantation of prosthetic devices. Forexample, in selecting a prosthetic heart valve, it is preferable toselect the largest size valve possible. A large effective valve orificeis preferable because it creates less resistance to forward flow andrequires the heart to do less work.

Traditional sizing of a heart valve annulus is performed by placing aknown diameter sizing apparatus into the annulus and observing the fitof the sizing apparatus. If the sizing apparatus appears to fit easilyinto the annulus, the sizing apparatus is retracted and a larger sizingapparatus is inserted. In some procedures, the native annulus isexpanded from its natural state due to the radial outward pressure of aprosthetic valve implanted within the native annulus. Unfortunately,known sizing apparatuses do not take into consideration the final,functional size of the annulus when expanded by the prosthetic valve.That is, these techniques cannot measure the size of a heart valveannulus when it is expanded under pressure.

SUMMARY

In one embodiment, an apparatus is provided for measuring an expandedinternal orifice of a patient. The apparatus can comprise anorifice-expanding device, a pressure-measuring device, and asize-measuring device. The orifice-expanding device can be located at ornear a distal end of the apparatus. The orifice-expanding device can beradially expandable from a first configuration to a second, expandedconfiguration to cause corresponding radial expansion of the orifice.The pressure-measuring device can be configured to measure a pressureapplied to the orifice by the orifice-expanding device. Thesize-measuring device can allow a user to measure a dimension of theorifice after it has been expanded by the orifice-expanding device. Themeasurement of the dimension can be obtained independently of thepressure measurement measured by the pressure measuring device.

In specific implementations, the size-measuring device can comprise acoiled member. The coiled member can surround at least a portion of theorifice-expanding device and can be configured to uncoil when theorifice-expanding device expands from the first configuration to thesecond configuration.

In specific implementations, the coiled member can have an outer facewith visual indicia that correspond to different dimensions formeasuring the size of the expanded orifice. In other specificimplementations, the coiled member can have a first end and a secondend, with the first end being attached to a portion of theorifice-expanding device. The position of the second end of the coiledmember relative to the outer face of the coiled member can identify thedimension of the expanded orifice.

In specific implementations, a shaft member can be connected to theorifice-expanding device and the size-measuring device can comprise awire member that surrounds at least a portion of the orifice-expandingdevice. The wire member can have a first end and a second end, with thefirst end being fixed in position relative to the orifice-expandingdevice and the second end having a marker that is free to movelongitudinally along the shaft. The position of the marker along theshaft can identify the dimension of the expanded orifice. In otherspecific implementations, the wire member can pass through openings inone or more bar members that are attached to the orifice-expandingdevice.

In specific implementations, the size-measuring device can comprise alocking member. The locking member can surround at least a portion ofthe orifice-expanding device, and can be configured to increase indiameter from a first position to a plurality of second positions. Whenthe locking member is expanded to one of the plurality of secondpositions, the locking member can lock in that position, therebypreventing the locking member from returning to the first position. Inother specific implementations, the locking member can be a one-waylocking member that permits an increase in radial size of the sizemeasuring member but prevents a decrease in radial size of the sizemeasuring member.

In specific implementations, the orifice-expanding device can be aninflatable balloon. In other specific implementations, thepressure-measuring device can measure the pressure exerted by theballoon based on the volume of fluid added to the balloon.

In specific implementations, the orifice-expanding device can have oneor more linkages that effect radial expansion of the orifice-expandingdevice, and the pressure-measuring device can comprise one or morestrain gauges positioned on the orifice-expanding device.

In another embodiment, a method can comprise accessing an internalorifice of a patient's body, placing an orifice-expanding device of asizing apparatus into the orifice, expanding the orifice-expandingdevice to cause it to exert a desired pressure against the orifice tocause the orifice to expand, and measuring a dimension of the expandedorifice independently of the pressure exerted by the orifice-expandingdevice.

In specific implementations, the orifice can comprise an annulus of aheart valve and the method further comprises selecting a prostheticheart valve based on the measured dimension of the annulus, andimplanting the heart valve in the annulus. In other specificimplementations, the act of measuring a dimension of the expandedorifice can be accomplished while the orifice-expanding device is in theexpanded orifice. In other specific implementations, the act ofmeasuring a dimension of the expanded orifice can comprise readingvisual indicia on the sizing apparatus and recording the measureddimension.

In other specific implementations, the sizing apparatus can comprise acoiled member surrounding at least a portion of the orifice-expandingdevice and which can uncoil upon expansion of the orifice-expandingdevice. The coiled member can have a first end and a second end, and thefirst end can be fixed relative to the orifice-expanding device. Thecoiled member can have visual indicia on a surface of the coiled member.The act of measuring a dimension of the expanded orifice can compriseobserving the position of the second end of the coiled member relativeto the visual indicia.

In other specific implementations, the sizing apparatus can comprise anelongated shaft and a movable indicator coupled to the orifice-expandingdevice and operable to move longitudinally of the shaft upon expansionof the orifice-expanding device. The act of measuring a dimension of theexpanded orifice can comprise observing the position of the movableindicator relative to a location on the shaft.

In specific implementations, the act of measuring a dimension of theexpanded orifice can be accomplished after the orifice-expanding deviceis removed from the body. In other specific implementations, the methodcan further comprise retaining the orifice-expanding device in anexpanding state after the act of expanding the orifice-expanding deviceand removing the orifice-expanding device from the body in its expandedstate in order to measure the dimension of the expanded orifice.

In specific implementations, the method can further comprise measuringthe pressure exerted by the orifice-expanding device. In other specificimplementations, the orifice-expanding device can be a balloon and theact of expanding can comprise inflating the balloon to expand theorifice. In other specific implementations, the orifice-expanding devicecan comprise one or more strain gauges and the method can furthercomprise measuring the strain on the orifice-expanding device when it isexpanded and determining the pressure exerted against the orifice by theorifice-expanding device from the measured strain. In other specificimplementations, the orifice-expanding device can comprise anon-cylindrical outer surface that generally corresponds to the shape ofthe orifice.

In another embodiment, a method can comprise radially expanding anorifice in a patient's body and indicating a dimension of the expandedorifice. The act of indicating the dimension of the expanded orificedoes not include calculating the dimension based on the pressure exertedby the orifice-expanding device against the orifice.

In specific implementations, the orifice can comprise an annulus of aheart valve and the method can further comprise selecting a prostheticheart valve based on the dimension of the annulus, and implanting theheart valve in the annulus.

In specific implementations, the act of radially expanding the orificecan comprise inserting an orifice-expanding device in the heart valveannulus and expanding the orifice-expanding device to expand theannulus. The method can further comprise measuring the pressure exertedby the orifice-expanding device against the annulus in order to expandthe annulus to a desired pressure.

In specific implementations, the act of radially expanding the orificecan comprise inserting an orifice-expanding device in the heart valveannulus and expanding the orifice-expanding device to expand theannulus. The act of indicating can comprise indicating the diameter ofthe expanded annulus after it is expanded by the orifice expandingdevice, and the act of implanting the heart valve can comprise insertingthe heart valve in the annulus and expanding the heart valve to expandthe annulus and anchor the heart valve in the expanded annulus. Thediameter of the expanded annulus after implanting the heart valve can beapproximately the same as the diameter of the annulus after it wasexpanded by the orifice-expanding device.

In specific implementations, the act of implanting the heart valve cancomprise inserting the heart valve in the annulus and expanding theheart valve to expand the annulus and anchor the heart valve in theexpanded annulus. The pressure exerted by the expanded heart valve canbe approximately the same as the desired pressure.

In another embodiment, an apparatus for measuring a heart valve annulusof a patient is disclosed. The apparatus can comprise expansion meansfor expanding the heart valve annulus and measuring means for measuringthe diameter of the expanded annulus. In other specific embodiments, theapparatus can further comprise means for measuring the pressure exertedby the expansion means against the annulus to allow expansion of theannulus to a desired pressure.

The foregoing and other objects, features, and advantages of theinvention will become more apparent from the following detaileddescription, which proceeds with reference to the accompanying figures.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a cross-sectional view of an illustration of a portion of ahuman heart with the aortic leaflets in the closed position.

FIG. 1B is a cross-sectional view of an illustration of a portion of ahuman heart with the aortic leaflets removed.

FIG. 2 is a perspective view of a device for sizing an orifice, with thedevice shown in an unexpanded configuration, according to oneembodiment.

FIG. 3 is an end view of the device of FIG. 2.

FIG. 4 is a view of the device of FIG. 2, with the device shown in anexpanded configuration.

FIG. 5 is an end view of the device of FIG. 4.

FIG. 6 is a partial view of a device for sizing an orifice with visualindicia used for measuring the size of the orifice.

FIG. 7 is a fluid pressurization device for use with a sizing devicethat has an expandable balloon member.

FIG. 8 is a cross-sectional view of an illustration of a portion of ahuman heart shown with a device for sizing an orifice positioned near anaortic valve.

FIG. 9 is a cross-sectional view of an illustration of a portion of ahuman heart shown with the device of FIG. 8 in an expandedconfiguration.

FIG. 10 is a side view of a device for sizing an orifice, with thedevice shown in an expanded configuration.

FIG. 11 is an end view of the device of FIG. 10.

FIG. 12 is a side view of a device for sizing an orifice, according toanother embodiment.

FIG. 13 is an enlarged view of the distal end portion of the deviceshown in FIG. 12.

FIG. 14 is a partial cross-sectional perspective view of an illustrationof a portion of an aorta shown with the device of FIG. 12 positionednear the aortic valve.

FIG. 15 is a partial cross-sectional perspective view of an illustrationof an aorta shown with the device of FIG. 14 in an expanded position.

FIG. 16 is a perspective view of a device for sizing an orifice,according to another embodiment.

FIG. 17 is a side view of a portion of a device for sizing an orifice,according to another embodiment.

FIG. 18 is a side view of a portion of a device for sizing an orifice,according to another embodiment.

DETAILED DESCRIPTION

It is often useful to obtain a size measurement of a human orifice. Suchsizing is particularly useful during or prior to implantation ofprosthetic devices where it can be desirable to obtain a tight fitbetween the prosthetic device and the orifice into which the prostheticdevice will be positioned. Traditionally, such sizing is performedwithout any consideration of the pressures that the prosthetic devicemay exert on the orifice during the implantation procedure or orificedimensional changes due to various physiological conditions (e.g.,systolic and diastolic pressures). If the prosthetic device is to beplaced into the orifice and then expanded to achieve a tight fit betweenthe prosthetic device and the orifice, the size of the orifice willexpand during such a procedure and such expansion should be taken intoconsideration when sizing the orifice. Thus, it is desirable to eithermeasure the size of the orifice at (1) pressures similar to, or somewhatless than, that which will be applied during implantation of theprosthetic device or (2) pressures that mimic actual targetedphysiological conditions to establish a baseline for bio-prosthesissizing. As used herein, the term “orifice” means any body orifice,annulus, or lumen within the body.

The aortic valve annulus is an example of an orifice that requiresaccurate sizing for the implantation of a prosthetic device. Surgicallyimplanted heart valves are traditionally sized so that they are smallenough to fit into the anatomical location, yet still large enough tofill the space when they are sewn to the patient's annulus. In somecircumstances, it may be desirable to secure the valve with anexpandable outer stent that exerts a radial outward force on the tissueof the annulus. The outward force exerted by the expanding stent candesirably enlarge the annulus, which allows a surgeon to implant alarger valve in a patient. A larger valve is generally desirable becauseit creates less resistance to forward flow and requires the heart to doless work.

By inserting a stent that expands the annulus, it is also possible toreduce or eliminate paravalvular leaks by forcing the elastic tissue inthe annulus to conform to the more rigid stent. In addition, the outwardradial force provided by the stent is directly proportional to thefrictional resistance to axial movement. Thus, by increasing the size ofthe valve, paravalvular leaks can be reduced or eliminated and the axialstability of the device can be improved.

With anatomical structures that have highly variable non-linear elasticmodulus that vary significantly from patient to patient, the sizing ofthe orifice when expanded under pressure can be particularly important.In such cases, the actual normal force that is critical to thefrictional resistance to axial movement of the valve for a particularpatient cannot be easily determined. To assure the selection of a valvethat will provide adequate frictional resistance, a sizing apparatus inparticular embodiments can be used to expand an orifice by anapplication of a radial force similar to, or somewhat less than, theforce that will be applied to the surrounding tissue by the deployedprosthetic device. The sizing apparatus desirably includes anorifice-expanding device that allows a surgeon to apply a desired levelof force to expand the native orifice, and a measuring device thatallows the surgeon to measure the size (e.g., diameter) of the expandedorifice at the desired level of force.

In particular embodiments, a sizing apparatus is provided that allows asurgeon to view the sizing apparatus and the orifice to be sized duringthe sizing procedure. By providing a sizing device that is capable ofbeing visually observed during expansion of an orifice, it is possibleto visually ensure that the device is located in the area of the anatomythat the user intends to measure. The sizing apparatus can also includea measuring device having visual indicia that allows the surgeon tomeasure the size of the expanded orifice while the distal end portion ofthe apparatus is still in the expanded orifice.

Embodiments of a sizing apparatus that can be used, for example, to sizean aortic valve annulus are discussed in greater detail below. FIG. 1Ais a cross-sectional view of an illustration of a portion of a humanheart. Native aortic valve 10 includes valve annulus 12 and nativeleaflets 14. Aortic valve 10 is located between the aorta 16 and theleft ventricle 18. FIG. 1B is another cross-sectional view of the humanheart. FIG. 1B is similar to FIG. 1A, but with the native leafletsremoved in preparation of receiving a prosthetic heart valve, such as asurgically implanted heart valve. Although the figures shown here depictthe sizing of orifices with various native structures removed (e.g., theaortic valve leaflets), the device for sizing orifices disclosed hereincan also be used, if desired, to measure orifices with such native orartificial structures intact. The sizing apparatus can also be adaptedto measure the size of other orifices or lumens within the body.

FIGS. 2 and 3 show views of an embodiment of a sizing apparatus 20 in anunexpanded configuration. Sizing apparatus 20 includes a handle portion22, fluid passageway, or fluid conduit, 24, shaft 26, balloon 28, andcoil member 30. Handle portion 22 and shaft 26 are desirably curvedand/or malleable (flexible) to facilitate use of sizing apparatus 20 andto provide improved access of the sizing apparatus 20 into the lowerportion of the aorta. Handle 22 also desirably has a grip surface, whichprovides a more comfortable and stable surface for the surgeon to holdonto during a sizing procedure. Shaft 26 passes through handle portion22 and is in fluid connection with fluid passageway 24. Alternatively,shaft 26 can contain another internal conduit that is in fluidconnection with fluid passageway 24.

Balloon 28 is attached to the distal end of shaft 26. Fluid passageway24 and shaft 26 deliver to the balloon 28 a fluid that is capable ofinflating balloon 28. Coil member 30 can be a thin sleeve of a flexiblematerial that is relatively non-elastic. For example, a thin sleeve of anon-elastic plastic film can be coiled around balloon 28. Desirably, thecoiled member is formed of a non-elastic material so that as it unwindsit is relatively uniform and constant in length. Coil member 30 can beformed of any suitable material, including, for example, plastics,non-elastic films, metals, or the like.

FIG. 3 is a bottom view of sizing apparatus 20. As seen in FIG. 3, thesize-measuring device of this embodiment comprises a coil member 30 iswrapped around (or coiled around) balloon 28. Coil member 30 has twoends. Coil member 30 is desirably attached to balloon 28 at the firstend 32. The first end can be attached to the balloon by any knownattachment methods, such as gluing, bonding, welding, stitching, orother mechanical fasteners. The second end 34 of coil member 30 islocated on the outside of the coil member. Coil member 30 is desirablyformed so that it is pre-stressed in a tightly wound coil, with secondend 34 pressed firmly against the outer surface of coil member 30.

FIGS. 4 and 5 show views of sizing apparatus 20 in an expandedcondition. To expand coil member 30, fluid from a fluid pressurizingdevice (such as the device shown in FIG. 7) passes through fluidpassageway 24, through the handle portion 22, through shaft 26, and intoballoon 28. As balloon 28 expands, coil member 30 uncoils, and secondend 34 changes position on the outside of coil member 30. That is, asballoon 28 expands, second end 34 recedes, or moves back, from itsunexpanded position and more of the outer surface of coil member 30 isexposed.

As shown in FIG. 6, sizing apparatus 20 can include pre-marked visualindicia, such as indicator lines 36, for measuring a dimension (e.g.,the diameter) of the expanded native orifice. The indicator lines 36 caninclude solid lines indicating a first set of sizes, e.g., 19 mm, 21 mm,and 23 mm, and dotted lines indicating a second set of sizes, e.g., 20mm and 22 mm. The indicator lines 36 are positioned so that they alignwith the second end of coil member 30 when the expandable member is inits expanded condition. The indicator lines and other related visualindicia can be printed on the outside of coil member 30 so that it isvisible to the operating surgeon during the sizing procedure. In thismanner, the diameter of the expanded coil member 30, and therefore theexpanded orifice, can be visually determined by observing where secondend 34 meets the indicator lines on the outside of coil member 30.

Balloon 28 can be expanded using any known fluid pressurizing devicethat is capable of expanding balloon catheters to known pressures. Forexample, FIG. 7 illustrates a known inflation device such as isdescribed in U.S. Pat. No. 5,713,242, which is incorporated by referenceherein. As described in more detail in U.S. Pat. No. 5,713,242, fluidpressurization devices utilize known volumes of fluid to inflate ballooncatheters to various measured pressures. Referring to FIG. 7, fluidpressurization device (or inflator device) 40 comprises a cylindricalsyringe body and fluid displacement chamber 42, a pressure monitoringgauge 44, and a knob 46. Knob 46 is turned to actuate an internalthreaded plunger that causes fluid to leave the fluid displacementchamber 42 and exit fluid pressurization device at connector 48.Connector 48 is fluidly connected to fluid passageway 24 of the sizingapparatus (shown, for example, in FIGS. 2, 4, and 6). Accordingly, asknob 46 is adjusted, fluid flows from fluid pressurization device 40,through the sizing apparatus, and into balloon 28. Using a fluidpressurizing device such as that disclosed in U.S. Pat. No. 5,713,242,the balloon can be inflated to a known pressure. Alternatively, apressure relief valve can be employed to make sure the correct pressureis used, which can eliminate the need for a pressure gauge.

FIG. 8 shows an illustration of sizing apparatus 20 being used to sizethe aortic valve annulus 12 of a human heart. Access to the heart can beachieved by any known surgical technique. For example, access to theaortic valve can be achieved by an upper mini-sternotomy. After gainingaccess to the aorta, the balloon 28 of the sizing apparatus 20 can beinserted into the space of the aortic valve annulus 12. Using handleportion 22, the sizing apparatus can be maneuvered until it ispositioned in the appropriate location for expansion and measurement ofthe valve annulus. A fluid pressurization device (such as describedabove) can be connected to fluid passageway 24 and fluid can be sentthrough the sizing apparatus to expand balloon 28. Balloon 28 ispreferably expanded to a pressure greater than 120 mm Hg, and morepreferably to a pressure greater than 250 mm Hg.

For certain applications, an implantable, radially-expandable valve maybe expanded by a balloon inflated to about 3800 mm Hg (5 atmospheres).Accordingly, it may be desirable to expand the sizing apparatus to apressure that approximates the pressure the valve annulus willexperience during expansion of the valve. In order to approximate thepressure that the annulus will experience under valve expansion, it isdesirable to apply the same pressure or less pressure than the annuluswill experience under valve expansion. Thus, it may be desirable toexpand balloon 28 to a pressure between about 200 mm Hg and 5320 mm Hg(7 atmospheres,) and more desirably between about 250 mm Hg and 500 mmHg.

Alternatively, it can be desirable to measure the maximum diameterachieved by the valve annulus during the cardiac cycle, which occurs atthe end of systole for the aortic valve. This measurement can then usedto establish a baseline for selecting the size of the bio-prosthesis. Todetermine the maximum diameter of the valve annulus, the sizingapparatus can be pressurized (or expanded) to mimic the physiologicalcondition of the annulus at its greatest diameter. Thus, the pressurethat is used to inflate (or expand) the sizing apparatus can be thepressure to actuate (open) the sizing apparatus plus approximatelybetween about 250 mmHg and 500 mmHg, and more preferably about 350 mmHg.This pressure range provides a pressure on the valve annulus that isequal to an estimated maximum physiological pressure seen by the aorticvalve annulus (approximately 140 mmHg) plus an additional amount toensure that the measured size of the annulus corresponds to a valve sizethat will provide a proper interference fit with the annulus, therebyreducing the likelihood of implant migration and providing improvedhemodynamic performance.

After balloon 28 is expanded to the desired pressure, a reading can beobtained from the indicator lines 36 of the sizing apparatus 20.Specifically, the indicator line that aligns with second end 34 of coilmember 30 identifies the size of the expanded coil member 30, whichcorresponds to the size of the expanded orifice. For example, if balloon28 is expanded and second end 34 of coil member 30 aligns with anindicator line that corresponds to a diameter of 22 mm, the expandeddiameter of the orifice can be determined to be 22 mm.

In this embodiment and in other embodiments discussed below, a surgeoncan use a pressure measurement or other pressure indicator as a meansfor determining how much the apparatus will be (or should be) expandedwithin the orifice. The measurement of the orifice size, however, can bedetermined independent of the pressure applied. For example, the sizemeasuring device 30 does not attempt calculate the size of an orifice bytranslating balloon pressure into a balloon diameter; rather, the sizemeasurement device performs the measurement of the orifice independentof the pressure applied, thereby providing a more accurate measurementof the orifice.

As discussed above, desirably, the size of the expanded orifice can bevisually determined in-situ by a surgeon by viewing the position of thesecond end 34 of coil member 30. By providing visual access to theexpanded orifice, in addition to knowing the amount of pressure appliedto the orifice (as discussed above), the surgeon can visually determinethe condition of the expanded orifice. For many applications, theelasticity of a particular orifice can vary greatly between patientsand, therefore, it is desirable, if not necessary, to be able todetermine the effect of the expandable member on the patient's orifice.This can be particularly true with orifices that are calcified orotherwise diseased. Variations in state of disease, as well asvariations in natural elasticity, can make it difficult to approximatethe amount of expansion desired in a particular application withoutfirst applying a force similar to the force applied by the devicesubsequently implanted in the annulus and then directly viewing thetreatment site for changes prior to implanting the prosthetic device inthe annulus.

If the access to the heart and anatomy of the patient permits it, asurgeon could also remove the sizing apparatus from the body, in theexpanded form and obtain the size of the expanded coil member in thatmanner. Alternatively, if a view of the coil member is obstructed by theanatomy of the patient, a surgeon could use other view enhancingequipment to obtain the size of the expanded coil member. For example, asurgeon could use a videoscope to see the markings on the coil membermore clearly.

Other markings techniques could be implemented that permit the surgeonto deflate the balloon, remove the sizing apparatus from the body, andthen determine the size of the earlier expanded coil member. Forexample, the coil member could be configured such that the second end ofthe coil member leaves a visible or otherwise observable mark at itslargest expanded location. A surgeon could then view this mark once thesizing apparatus is removed from the body and the expanded size of thesizing apparatus could be determined in this manner.

FIGS. 10 and 11 illustrate another embodiment of a sizing apparatus witha coil member 50. Coil member 50 includes a ratcheting-type lockingmechanism 52. The locking mechanism 52 in the illustrated embodimentcomprises a radially protruding ramp-like member that extends intospaces 54 in coil member 50. As balloon 28 expands, coil member 50expands and locking mechanism 52 locks coil member in the expandedposition. Thus, spaces 54 provide locking mechanism 52 with a pluralityof positions in which it can lock. The locking mechanism in theillustrated embodiment is a one-way locking mechanism. Accordingly,although coil member 50 can enlarge from a first position with arelatively small radial size, to a number of positions with a largerradial size (as defined by spaces 54), the locking mechanism 52 preventscoil member 50 from returning to the first position, or to otherradially smaller positions once it has been enlarged.

Thus, when coil member 50 reaches its maximum expansion with the lockingmechanism 52 extending into an aperture 54, locking mechanism 52maintains coil member 50 in that position. Coil member 50 can includevisual sizing indicia as discussed above. Alternatively, coil member 50can be removed from the body and the size determined by some othermeasurement technique.

FIGS. 12-14 illustrate another embodiment of a sizing apparatus 60.Sizing apparatus 60 includes a handle portion 62, a fluid passageway 64,a shaft 66, and a balloon 68, each of which are similar to thoseelements discussed above with regard to the other embodiments. Sizingapparatus 60 also includes an expandable sizer 70. Expandable sizer 70is desirably shaped so that it approximates the shape of the annulusthat is to be measured. In this example, expandable sizer 70 is shapedin a tri-lobe configuration that approximates the shape of the aorticvalve annulus.

The sizer 70 comprises a hub 71 mounted to the distal end of the shaft66 adjacent to balloon 68, a plurality of elongated arms 76 (three inthe illustrated embodiment) attached to and extending from the hub 71,and a plurality of expanding portions 72 (three in the illustratedembodiment) mounted to the distal end portions of the arms. Theexpanding portions 72 extend circumferentially about balloon 68 and haveouter surfaces that desirably are shaped to generally conform to thetri-lobe shape of the aortic valve annulus. A locking mechanism 74 canbe mounted on the inner surfaces of the expanding members 72.

As shown in FIG. 14, expandable sizer 70 of sizing apparatus 60 can beinserted into the aorta 76 to determine the size of the aortic valveannulus in an expanded condition. As balloon 68 expands, it exerts aradial force on the expanding portions 72 (only two are shown in FIGS.12-14 for clarity). Expanding portions can be interconnected via lockingmechanisms 74. Any number of arms can be used to secure the expandingportions 72 to the shaft 66; however, desirably, there are two or morearms. In addition, while three expanding portions 72 are used in theillustrated embodiment, a greater or fewer number of expanding portionscan be used.

As seen in FIG. 14, locking mechanisms 74 can have grooves that lock theexpandable sizer 70 in any of a plurality of expanded positions. Inparticular, the grooves (or teeth) shown in FIG. 14 mate with opposinggrooves (or teeth) on the inside of expanding portions 72, permittingthe expanding portions to move away from one another, while at the sametime preventing them from collapsing back towards each other after theballoon 68 is deflated. FIG. 14 shows expanding sizer 70 after balloon68 has been expanded and subsequently deflated. The grooves of thelocking mechanisms 74 have effectively locked the expandable sizer 70into an expanded position. Accordingly, a surgeon can then remove thesizing apparatus 60 from the patient's body and determine the size ofthe expanded orifice under the known pressure that was applied byballoon 68. The size of the expanded orifice can be determined by anymeasuring technique, including, for example, fitting the removed sizerinto a secondary hole gauge to determine the size of the expandedportions. The secondary hole gauge could include various size openingsand the surgeon can determine the size of the expanded portions byplacing the sizer in the various openings until the proper size of theexpanded portions is determined.

In addition, one or more strain gauges 78 can be positioned on one ormore of arms 76. Strain gauges 78 can be electrically connected to aprocessor that can be housed in the handle. As can be seen, outwardradial movement of expanding portions 72 causes corresponding outwarddeflection of the distal ends of arms 76, which in turn increases thestrain on the arms. The processor measures the strain on arms 76 andcalculates a value corresponding to the pressure or force applied to thevalve annulus by the expanding portions 72 based on the measured strain.Strain gauges 78 can be any of a variety of commercially availablestrain gauge, such as, for example, metal foil type strain gauges. Thestrain gauge can be used in combination with the pressure monitoringgauge (discussed above) to determine the amount of pressure applied tothe expanding portions 72, or it can be used independent of the pressuremonitoring gauge. The sizing apparatus can include a visual alphanumeric display located on the handle or at another convenient locationto display the pressure applied by the sizer against the annulus. Theprocessor can be any type of processor that can receive electricalsignals from the strain gauges and calculate a value corresponding topressure or force.

In another embodiment, the balloon can be omitted and the expandingsizer 70 can be mechanically expanded to the appropriate size within theannulus. Referring to FIG. 15, a mechanically expandable sizingapparatus 80, according to one embodiment, is disclosed. Expandingportions 82 can be interconnected to each other via locking mechanisms84 as discussed above. However, instead of expanding the expandingportions using a balloon, expanding portions can be mechanicallyexpanded. For example, pull wires 86 can extend through arms 90 andthrough shaft 88 to a handle (not shown). The pull wires 86 can beattached to the handle, which can include any number of mechanicalmechanisms for applying pressure to pull wires 86. For example, thehandle can have a rotatable knob coupled to the pull wires to increaseand decrease tension on the pull wires by rotation of the knob. Theapplication of tension on pull wires 86 causes the expanding portions 82to expand radially outwardly from one another. Since there is no knownfluid expansion to determine the amount of pressure that is beingapplied to the sizing apparatus, one or more strain gauges 92 can bepositioned on arms 90. Strain gauges 92 can be electrically connected toa processor that can receive signals from the strain gauges andcalculate a value corresponding to the pressure applied by the expandingportions 82 against the surrounding tissue, as described above. Ratherthan pull wires, any number of known mechanical techniques can be usedto mechanically expand the sizing apparatus.

For example, as shown in FIG. 16, various linkages can be used to causeradial expansion of the expanding portions of a sizing apparatus.Mechanical expanding sizer 100 comprises a handle portion 102, expandingportions 104, and a shaft 106. An internal extension member 108 extendslongitudinally inside of shaft 106 from the handle portion 102 tolinkages 110. Linkages 110 are connected to expanding portions 104 suchthat upon longitudinally movement of extension member 108 toward handleportion 102, the linkages are forced radially outward, therebyincreasing the perimeter size of the expanding portions 104. Arms 112connect expanding portions 104 to shaft 106. Strain gauges 114 can beattached to arms 112 and electrically connected to a processor that canbe stored in handle portion 102. By obtaining strain measurements ofarms 112, the amount of pressure applied by expanding portions 104 tosurrounding tissue can be determined. After expanding an orifice at adesired pressure by expansion of expanding portions 104, the sizer 100can be removed from the orifice and the size of the orifice (asdetermined by the expanding portions 104) can be measured. Desirably,after the orifice is expanded, the extension member 108 can be securedin place, thereby maintaining the position of the expanding portions 104while the sizer 100 is removed from the orifice. Thus, expandingportions 104 can be expanded to apply a known pressure to the orificeand a measurement of a dimension (e.g., diameter) of the expandedorifice can be determined.

Expanding portions of a mechanical expanding sizer can be cylindrical ornon-cylindrical. As shown in FIG. 16, expanding portions 104 can beconfigured to have a shape that generally corresponds to the shape ofthe orifice to be measured. For example, expanding portions 104 can havea tri-lobe configuration that corresponds with the shape of an aorticvalve annulus, as shown in FIG. 16. The non-cylindrical shape canfurther be extended to the other embodiments discussed above, and neednot be limited to the mechanical expanding sizer shown in FIG. 16. Forexample, a non-cylindrical shaped balloon member can be used as theexpandable member. Alternatively, a sizing apparatus can compromise asize-measuring device having a non-cylindrical outer surface. Thesize-measuring device can be disposed around a cylindrical balloon,which is inflatable to cause the non-cylindrical size measuring deviceto expand.

In another embodiment, an indicator can be provided on a portion of thesizing apparatus other than the orifice-expanding device, such as theshaft or the handle, so that the size of the expanded orifice can bereadily determined by a surgeon while the sizing apparatus is still inthe body without requiring direct visual access to the portion of thesizing apparatus within or near the orifice. FIG. 17 shows an embodimentthat permits a surgeon to measure an orifice without direct visualaccess to the portion of the apparatus that is placed in the body. Asshown in FIG. 17, a sizing apparatus 120 comprises a handle portion (notshown, but similar to those discussed above), a shaft 122 with a lumen124 passing through shaft 122, and a balloon 128 fitted on the end ofshaft 122. Balloon 128 is in fluid connection with a fluid passageway(as discussed above) so that the balloon 128 can be expanded to size anorifice.

A tag indicator 126 can be disposed on an outside surface of shaft 122.Alternatively, tag indicator 126 can be disposed inside (or partiallyinside) shaft 122 with a window member making the indicator visible fromoutside of shaft 122. A wire 132 is connected to tag indicator 126 andpasses through the lumen 124 of shaft 122. Wire 132 then passes throughopenings on bars 130, which can be mounted on the outer surface ofballoon 128 at regular intervals around balloon 128, and forms a coilextending around the balloon. A distal end of the wire 132 is secured toone of the bars 130. When balloon 128 is expanded, the coil of wire 132that wraps around balloon 128 is increased and the tag indicator 126 ispulled closer to balloon 128, as shown by the arrows of FIG. 17. Thus,the outer diameter (or size) of balloon 128 can be determined by thelocation of tag indicator 126 along the shaft 122. Desirably, shaft 122includes visual indicia (or graduations) so that the size of theexpanded balloon 128 can be determined by observing the location of tagindicator 126 with reference to the indicia on shaft 122. The visualindicia desirably are provided along a section of the shaft that allowsthe surgeon to observe the position of the indicator 126 relative to thevisual indicia while the expanded balloon is still within the orifice.

FIG. 18 is another embodiment of a sizing apparatus 120 that includes awire 132 that is connected to a tag indicator 126 to determine theexpanded size of the balloon 128. The embodiment of FIG. 18 is similarto that of FIG. 17, except that wire 132 is attached to a coil member134 rather than to bars 130. The coil member 134 can comprise anon-elastic, flexible piece of material, similar to coil member 30 shownin FIGS. 2-5. As shown in FIG. 18, the wire 132 is wound around theballoon to form a wire coil and the coil member 134 is wound over thewire coil with a distal end of the wire secured to the inner surface ofthe coil member 134. As the coil member 134 and the wire coil expandwith the balloon 128, tag indicator 126 is pulled towards the balloon128, as shown by the arrows in FIG. 18. Thus, just as above, the tagindicator 126 can be used to determine the size of the expanded balloon128, which also corresponds to the size of the orifice under thepressure applied by the expanded balloon.

As discussed above, sizing determinations can be made visually by theimplanting surgeon. That is, the implanting surgeon can observe markingson the expanding device in-situ and determine the size of the expandedannulus. Alternatively, the implanting surgeon can remove the expandeddevice from the patient and either visually determine the appropriatesize based on markings on the device or measure the expanded device insome other manner (such as, for example, by fitting the expanded deviceinto pre-sized hole gauges as discussed above). In either case, however,it is desirable that the surgeon be able to visually observe theexpanded orifice to make a determination as to whether the orifice issufficiently expanded.

Sizing can also be achieved without visually observing the sizingapparatus, such as by taking readings off a tag indicator or from astrain gauge as discussed above. Alternatively, sizing can be determinedby radiography or echocardiography. This would be especially useful fora sizing apparatus that is deployed via a catheter and that must bedeflated or contracted before removal from the body can be achieved.

When implanting valves, surgeons often find that the first selectedvalve is too small and that the patient would benefit from upsizing to alarger valve. By using the sizing apparatus and method described above,an implanting surgeon can determine the valve size that will beappropriate when the annulus is expanded. Accordingly, the surgeon willnot have to experiment with various smaller size valves before findingthe valve that is most appropriate to the particular size annulus.Moreover, not only can the surgeon determine the size of the valve thatwill properly fill the annulus, but the surgeon can determine the sizeof the valve that will be large enough to exert sufficient frictionalresistance to axial movement.

Any standard heart valve surgery techniques can be used to gain accessto the heart to obtain the measurements described above. For example,the heart can be accessed by traditional surgical approaches, such as asternotomy or a thoracotomy. Alternatively, the heart can be accessedthrough minimally invasive heart valve surgery, such as an uppermini-sternotomy (for aortic valve replacement) or a lowermini-sternotomy (for mitral valve replacement).

In view of the many possible embodiments to which the principles of thedisclosed invention may be applied, it should be recognized that theillustrated embodiments are only preferred examples of the invention andshould not be taken as limiting the scope of the invention. Rather, thescope of the invention is defined by the following claims. We thereforeclaim as our invention all that comes within the scope and spirit ofthese claims.

We claim:
 1. An apparatus for measuring an expanded aortic valve annulusof a patient, the apparatus comprising: a proximal handle having a shaftextending distally therefrom along a longitudinal axis; anorifice-expanding device located at or near a distal end of the shaft,the orifice-expanding device having a hub mounted to a distal end of theshaft and three arms evenly spaced around the axis connected to the huband extending therefrom in a distal direction to distal ends of thearms, the distal end of each arm being connected to one of threecircumferentially-spaced expanding portions having outer surfaces, theexpanding portions being configured to move radially outward withrespect to each other and each being radially expandable from a firstconfiguration to a second, expanded configuration to cause the outersurfaces to contact and radially expand an aortic valve annulus, whereinexpansion of the expanding portions causes the distal ends of the armsto flex outward; a pressure-measuring device configured to measure apressure applied to the aortic valve annulus by the outer surfaces ofthe expanding portions in the second, expanded configurations; and asize-measuring device that allows a user to measure a dimension of theaortic valve annulus after the annulus has been expanded by theexpanding portions, wherein the size-measuring device operatesindependently of and does not require the pressure measured by thepressure measuring device.
 2. The apparatus of claim 1, wherein theorifice-expanding device includes an inflatable balloon positionedwithin the expanding portions and configured to force the expandingportions outward and thus circumferentially away from each other.
 3. Theapparatus of claim 2, wherein the pressure-measuring device includes apressure monitoring gauge that measures the pressure exerted by theballoon on the expanding portions.
 4. The apparatus of claim 3, furtherincluding one or more strain gauges positioned on one or more arms formeasuring the strain experienced by the arms and providing a secondarymeasure of the pressure exerted by the balloon on the expandingportions.
 5. The apparatus of claim 1, wherein the pressure-measuringdevice comprises one or more strain gauges positioned on one or morearms.
 6. The apparatus of claim 1, wherein the orifice-expanding devicehas one or more mechanical linkages within the expanding portions thateffect radial expansion of the expanding portions.
 7. The apparatus ofclaim 1, further including a visual alpha numeric display located on thehandle that displays the pressure applied to the aortic valve annulus.8. The apparatus of claim 1, wherein the size-measuring device comprisesa secondary hole gauge having various size openings configured toreceive the expanding portions such that the size of the expandingportions may be determined by placing the expanding portions in thevarious openings until the proper size of the expanding portions ismatched.
 9. The apparatus of claim 1, wherein the outer surfaces of theexpanding portions are shaped to conform to the tri-lobe shape of theaortic valve annulus
 10. The apparatus of claim 1, wherein the expandingportions are interlocked by locking mechanisms that permit the expandingportions to move away from one another, while at the same time thelocking mechanisms prevent the expanding portions from collapsing backtowards each other.
 11. An apparatus for measuring an expanded aorticvalve annulus of a patient, the apparatus comprising: a proximal handlehaving a shaft extending distally therefrom along a longitudinal axis;an orifice-expanding device located at or near a distal end of theshaft, the orifice-expanding device having a hub mounted to a distal endof the shaft and a plurality of arms evenly spaced around the axisconnected to the hub and extending therefrom in a distal direction todistal ends of the arms, the distal end of each arm being connected toone of a plurality of circumferentially-spaced expanding portions havingouter surfaces, the expanding portions being configured to move radiallyoutward with respect to each other and each being radially expandablefrom a first configuration to a second, expanded configuration to causethe outer surfaces to contact and radially expand an aortic valveannulus, wherein expansion of the expanding portions causes the distalends of the arms to flex outward; one or more strain gauges positionedon one or more arms configured to measure a strain experienced by theflexed arms and providing a measure of the pressure exerted by the outersurfaces of the expanding portions on the aortic valve annulus in thesecond, expanded configurations; and a size-measuring device that allowsa user to measure a dimension of the aortic valve annulus after theannulus has been expanded by the expanding portions, wherein thesize-measuring device operates independently of and does not input fromthe strain gauges.
 12. The apparatus of claim 11, wherein the shaft ismalleable or flexible.
 13. The apparatus of claim 11, wherein theorifice-expanding device has one or more mechanical linkages within theexpanding portions that effect radial expansion of the expandingportions.
 14. The apparatus of claim 11, wherein the orifice-expandingdevice includes an inflatable balloon positioned within the expandingportions and configured to force the expanding portions outward and thuscircumferentially away from each other, and further including a pressuremonitoring gauge that measures the pressure exerted by the balloon onthe expanding portions and provides a secondary measure of the pressureexerted by the expanding portions on the aortic valve annulus.
 15. Theapparatus of claim 11, further including a visual alpha numeric displaylocated on the handle that displays the pressure applied to the aorticvalve annulus.
 16. The apparatus of claim 11, wherein the strain gaugesare electrically connected to a processor housed in the handle, theprocessor being configured to receive electrical signals from the straingauges and calculate a value corresponding to the pressure exerted bythe expanding portions on the aortic valve annulus in the second,expanded configurations.
 17. The apparatus of claim 11, wherein thesize-measuring device comprises a secondary hole gauge having varioussize openings configured to receive the expanding portions such that thesize of the expanding portions may be determined by placing theexpanding portions in the various openings until the proper size of theexpanding portions is matched.
 18. The apparatus of claim 11, whereinthe expanding portions are interlocked by locking mechanisms that permitthe expanding portions to move away from one another, while at the sametime the locking mechanisms prevent the expanding portions fromcollapsing back towards each other.
 19. The apparatus of claim 18,wherein the locking mechanisms include grooves or teeth that mate withopposing grooves or teeth on the inside of the expanding portions. 20.The apparatus of claim 11, wherein there are three arms and threeexpanding portions, and the outer surfaces of the expanding portions areshaped to conform to the tri-lobe shape of the aortic valve annulus.